Along with the "GoPro Hero 3 Aux (3.5mm) Mic Adapter" this lead is used to connect an intercom (Peltor / Sparco / OMP / Stilo etc) to a GoPro HERO4, HERO3+ or HERO3 camera to enable the driver / co-driver communication to be recorded. This 3.5mm Jack plug to single RCA phono cable is supplied in a 1.2 meter length.